Contingent screening for Down syndrome completed in the first trimester: a multicenter study.

Area of Science:

• Prenatal diagnostics
• Genetics
• Maternal-fetal medicine

Background:

• First-trimester screening for Down syndrome is crucial for early detection.
• Combined screening (nuchal translucency and serum analytes) is a standard method.
• Intermediate-risk results necessitate further assessment to optimize diagnostic accuracy.

Purpose of the Study:

• To evaluate a novel contingent screening strategy for Down syndrome in the first trimester.
• To compare the efficacy and feasibility of contingent screening versus standard combined screening.
• To assess the impact on false-positive rates and detection rates.

Main Methods:

• A contingent screening strategy was implemented in nine healthcare centers.
• Pregnant women underwent first-trimester combined screening.
• Intermediate-risk cases were reassessed using secondary ultrasound markers (nasal bone, ductus venosus, tricuspid flow).
• Women were stratified into high-intermediate and low-intermediate risk subgroups.

Main Results:

• The contingent strategy reduced the false-positive rate from 3.0% to 1.3-1.8% (P < 0.001).
• Detection rates for Down syndrome remained unaffected (75-79% with contingent vs. 76% without).
• Only 45% of intermediate-risk patients completed the second screening step due to varied uptake and preference for invasive testing.

Conclusions:

• The first-trimester contingent screening strategy effectively reduces false positives without compromising Down syndrome detection.
• Low patient compliance with the secondary screening steps poses a challenge for implementation.
• Further research is needed to address compliance issues for broader population applicability.